emitter.js

function emitter(obj){
    var store = {}
    obj.on = function (e, cb) {
       add(e, cb, true)
    }
    obj.one = function (e, cb) {
       add(e, cb, false)
    }
    obj.off = function (e) {    
        delete store[e]
    }
    obj.emit = function (e) {
        var events = store[e] || []
        var args = Array.prototype.slice.call(arguments, 1)
        events.forEach(function(cb, i) {
            cb(args, i)
        })
    }
    return obj
    
    function add(e, cb, t) {
        store[e] = store[e] || []
        store[e].push(function (args, i) {
            cb.apply(obj, args)
            if (!t) store[e].splice(i,1)
        })
    }
}
 
var a = emitter({
    some: 123
})
a.on('roof-on-fire', function () {
   console.log('put the fire', this.some)
})
a.one('roof-on-fire', function (data) {
   console.log('call the fireman', data)
})
a.emit('roof-on-fire', { address: '560, Mission st.'})
a.off('roof-on-fire')